The type of retractor normally used at present includes a pair of mutually separable tissue-restraining plates or wings. The retractor is first inserted into the operation wound, often in the form of an incision, with the restraining plates lying contiguous with one another, such that the outer surfaces of the plates are in abutment with the mutually-opposing "walls" of the incision, whereafter the plates are forced apart sufficiently for the field of operation to be at least slightly accessible to the surgeon.
However, the restraining wings or plates of the known retractor, which bear against the walls of an operation wound and function to hold the wound open have a vertical extension such that the plates extend from the bottom of the wound up to the surface of the surrounding skin, even when the operation wound/incision is relatively deep. Thus, the vertical extension of the retractor plates covers the walls of the operation wound over the whole of their depth, including the uppermost layer of skin and associated fascia.
One problem in this regard, however, is that the fascia is far less elastic than the inwardly-lying muscular tissue, and consequently the separating force which the retractor needs to exert between the walls of the operation wound (when the retractor is adjusted to its wound widening and restraining state) is determined primarily by the smaller elastic resistance of the fascia. It has also been found that a retractor whose restraining plates have the aforesaid vertical dimensions has a pronounced tendency to slide upwards and out of the operation wound as a result of tension in the fascia. This tendency is, of course, particularly problematic during the course of an operation, since it necessitates repeated adjustment of the position of the retractor. Furthermore, due to the structural design of this known retractor, with mutually parallel and mutually separable wound-opening and wound-restraining plates, this known retractor causes muscular atrophy as a result of the high surface abutment pressure which prevails between muscle and the respective vertical front and rear edges of the restraining plates, this abutment being essentially a line contact between said edge and said muscle.
Another problem, which is closely related to the conditions which prevail in an operation in which the surgical section or wound area lies in the region of the patient's spine is that the spine vertebrae have projections (spinous and transverse spinelike processes) which are seated on the vertebrae arch, which in turn is seated on the body of vertebrae.
The retractor should therefore be constructed so as to provide sufficient space not only for the spine-vertebrae but also for the spinal vertebrae arches with the spinous and transverse spinelike processes of the vertebrae.